As is well-known, mining operations in the past for recovering various metals (e.g., lead and copper) have utilized high grade ore deposits where possible. Many of these deposits have been exhausted and mining of lower grade ores is increasing. The processing of these leaner ores consumes large amounts of time, labor, reagents, power and water with conventional processing.
In addition to the increased expense associated with the extraction of these metals from low grade ores, proposed processes for separation of certain of the sulfide ores are technically very difficult and involve elaborate and expensive equipment. In many cases the expense incurred by such separation would be greater than the commercial value of the metal, such that the mineral recovery, while theoretically possible, is economically unfeasible.
Our copending patent applications Ser. No. 086,830 filed Oct. 22, 1979 entitled "Process for Beneficiating Sulfide Ores" and Ser. No. 921,583 filed July 3, 1978 entitled "Process for Beneficiating Oxide Ores" teach the treatment of these ores with a metal containing compound under conditions such as to selectively enhance the magnetic susceptibility of the mineral values to the exclusion of the gangue, allowing for a separation of these values from the gangue. However, the presence of a particular impurity can have a profound effect on this type of process. More particularly, it has been found that the presence of elemental sulfur has an adverse effect on the recovery of mineral values in a process which enhances the magnetic susceptibility of the mineral values. Pretreating the raw ore to remove at least a portion of the elemental sulfur present, and thereafter selectively enhancing the magnetic susceptibility of the mineral values so that they may be physically separated from the gangue, substantially enhances the effectiveness of the separation of the mineral values from the gangue.